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What are the considerations for landing on ice runways?
In Greenland there are a number of ice runways and I have heard that it is no difficulty landing on them. One would think they would be slippery and the aircraft might slide off the runway or ground loop. However apparently that does not happen.
Are there any special considerations for landing on an ice runway? Is there an increase in minimum landing distance?

In Greenland there are a number of ice runways and I have heard that it is no difficulty landing on them. One would think they would be slippery and the aircraft might slide off the runway or ground loop. However apparently that does not happen.

Yes it does.  Go to Youtube and search for "Alton Bay Ice Runway" for examples.

Are there any special considerations for landing on an ice runway?

First, understand that you are making a short field landing, NOT a soft field landing.  A soft field landing (well, mine anyway!) will eat up much more runway length.  Ice is hard, and you can hammer it down if necessary.
Second, do not use your brakes until under about 5 knots. Use aerodynamic braking instead.  Yoke full back on the ground.

Is there an increase in minimum landing distance?

Yes!  Aerodynamic braking is pretty ineffective below 20-30 knots.

First one has to understand that the gamut for ice runways is very expansive.  Consider in the case of a grass runway, there is tall grass, short grass, rough surface, rolled surface, legumes (like clover) or grasses like Kentucky Bluegrass.  All these factors, and more change the nature of a runway. In the arctic, ice runways are used, particularly at some outposts where bringing in paving materials is cost prohibitive, and where the temperatures are stable enough for ice.
Given the kind of ice, landing on an ice runway can be like landing on concrete, or it can be like landing on a roughly plowed, refrozen country road. So the pilot (and ground crew) observations and planning are more significant than landing at the local strip of concrete.
If the ice is a frozen lake, then having knowledge of the thickness, and nature of the ice is important. If on a river, how smooth is it? If with moving water, are there pressure ridges, etc.
From personal experience, I have a couple of stories.  One time I landed at Martinsburg WV, after 1" of clear ice.  I needed to land, the tanks were getting low, DC was a mess WX wise, and Martinsburg was the best option. I landed (27 or 28, I forget the exact runway), stopped on the runway, and FSS had the FBO bring the fuel truck out to fuel me.  The runway had a candy coating, and was slick.  After fueling, I took off from where I stood. Oh, I forgot to mention that the winds were something like 280 at 40 gust 55. It worked, and the line personnel were great.
The next story dates back to the Winter Olympics at Lake Placid. Unable to fly into Lake Placid, I did what we had done dozens of times before.  Landed on Saranac Lake, and tied the plane down at my friends boat dock. A plow was handy if needed to clear a portion of the lake for takeoff.
Each of those were a higher workload than landing at an ice runway at a research facility in the arctic.  But they are all doable, and just need appropriate planning, and skills.
So to prepare for ice runways, be adept at soft, short, and everything in between.  And get used to the different types of ice, and what they look like, and how you will land on them.

Flight Safety Foundation FSF mission includes:

Promote and facilitate the global application of leading aviation safety assessments, standards and practices.
Develop global solutions to key aviation safety challenges

They analyzed runway excursions and published the "Approach and Landing Accident Reduction"(ALAR) toolkit, which is explained on SKYbary (a website fed by Eurocontrol).
The part of ALAR related to landing on iced runway is the Briefing Note 8.3: Landing Distances.
The document is a rich one, I'm extracting this part of a figure about landing distance factor:

The reference (factor 1) is without reverse thrust, and no contamination. A wet runway would require adding 40%, an iced runway adding 250%.

Although runway contamination increases rolling resistance and
  spray-impingement drag (i.e., drag caused by water or slush sprayed by
  tires onto the aircraft), it also affects braking efficiency.
The following landing distance factors are typical:
•  Wet runway: 1.3 to 1.4;
  •  Standing-water or slush-contaminated runway: 2.0 to 2.3;
  •  Compacted-snow-covered runway: 1.6 to 1.7; and,
  •  Icy runway: 3.5 to 4.5.

While this answer focuses on iced runway, Antarctica and Greenland runways are mostly compacted snow. Runways can be prepared using low ground pressure tractors. Aircraft can be fitted with skis:

Source: William Colgan
When landing on surface with small braking coefficient, you don't want forces to be very asymmetric (reversers, spoilers, or brakes).


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How to verify the runway numbers in a systematic way given the high workload during landing?
I have never had a runway number verification on my checklists because normally the landing checklist is completed and stowed by the time I am on short final and can clearly see the numbers.
However, after seeing that Harrison Ford just landed on a taxiway and I know commercial jets have done the same thing from time to time, I am considering a checklist item. One issue is not just the taxiways, a lot of larger airports and big airfields like Oshkosh have multiple parallel runways with right/left designations so it can get pretty confusing. The whole problem is that normally when I am on final and swooping in everything is happening fast and I do not have available bandwidth to be looking at a checklist, I have to be laser focused on making the landing and watching for traffic.
Any suggestions how to verify the runway in a systematic way given the constraints?

Oshkosh doesn't have any parallel runways or left/right designations. Oshkosh is a 20 minute flight from my home base. It's typically uncontrolled and has a pretty simple layout.

@RonBeyer It's obviously not normal, but Oshkosh is configured for parallel runway ops during EAA AirVenture. You can see it in the 2016 NOTAM, for example.

@Pondlife Yeah, they are controlled (by volunteers) and open a taxiway as a runway during AirVenture. They also assign colored dots for touchdown so they can sequence landings closer. That week in July/August is pretty out-of-the-ordinary for a special event. It is the one week a year I refuse to fly, especially after talking about horror stories with my CFI.

There are a few common (?) techniques you could use, although how you work them into your actual checklists is up to you. Here are some that I've been taught, there are probably more:
Tune the localizer and/or load an approach
Pros: reliable and accurate (if you set the avionics up right) because it gives you guidance for a specific runway
Cons: can lead to fixation on instruments when you should be looking outside; not every runway has an approach; your aircraft may not have the necessary avionics; may be awkward or distracting to set up and verify
Set the heading bug to runway heading
Pros: many pilots do this for takeoff, so it's a familiar check; works for any runway; convenient if you go around and are told to "fly runway heading"
Cons: doesn't uniquely identify a parallel runway
Write the runway number on your kneeboard
Pros: simple; easy to glance down at quickly
Cons: none that I can think of, unless you don't have a kneeboard
Or use all three techniques together, of course.
ATC could still change your landing clearance, or something else could force a change of plan, but stuff happens and you just have to deal with it. Personally I like the localizer/approach method at night and/or at an unfamiliar airport, otherwise I'll just write down the runway number on my kneeboard.

And, as that is specifically the question, 2 also does not prevent you from landing on a taxiway (parallel to the intended runway).

The FAA issued a NOTAM https://notams.aim.faa.gov/lta/main/viewlta?lookupid=1396671390068774785 in December of 2016 that deals with this issue.
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
OSG Western Service Area
Issued: 12/08/2016 1428 (UTC) Effective: 12/09/2016 1200 (UTC)
OSG Western Service Area Letter to Airmen: LTA-OSGW-15
Subject: Wrong Surface Landings and Departures
Cancellation: 12/09/2018 1200 (UTC)
Events in which an aircraft lands or departs on the wrong runway, a taxiway or lands at the wrong airport tend to be among the highest-profile and most dangerous events in aviation. These events have been occurring at an average rate of about 24 per year, increasing to over 60 in 2016.
Notable examples include:
• Seattle-Tacoma International (SEA), where a B737 landed on a parallel taxiway between two parallel runways.
• Boise Air Terminal/Gowen Field (BOI), where an A319 correctly read back the runway landing clearance but landed on the parallel runway.
• McCarran International (LAS), where an A320 was cleared to land runway 19R but landed on runway 19L.
Causal Factors:
The common denominator for most wrong surface landings/departures was the lack of situational awareness, with closely-spaced parallel runways, off set parallel runways, or taxiways which run parallel with runway.
Wintertime flying conditions, including:
• Sun lower on the horizon.
• Snow/water/ice on airport surfaces combined with lower visibility due to storms/fog.
• Closely-spaced parallel runways,
• Parallel runways with offset thresholds and a parallel taxiway abeam runway.
• Not comprehending/following the control instructions of Air Traffic Control (ATC).
• Controller workload or radar limitations which preclude timely intervention by ATC.
What can pilots do:
• Familiarize yourself with the airport to the maximum extent possible by reviewing pictures, maps and diagrams of the airport design.
• Look for offset runway thresholds, parallel runways (especially if closely-spaced), etc.
• Be familiar with the primary arrival runway.
• Be cognizant of adjacent or nearby airports, particularly ones with similar runways.
• Make sure all ATC instructions and clearances are clearly heard and understood. Make sure you give a proper read-back, if unsure, ask ATC to repeat the instructions or clearance again and don’t hesitate to ask questions about anything you feel requires clarification.
• Confirm that you have correctly identified the destination airport before reporting the airport/runway in sight, especially at night or when weather or environmental conditions might make precise identification more difficult.
Finally: Below are some depictions of what you may encounter during your flight. Remember to LOOK, LISTEN, and FOCUS -- the actions YOU take not only affect your safety, but also the safety of OTHERS.
[This image from the NOTAM looks a lot like the runway at John Wayne]

I don’t use checklists when taking off and landing, but I do use acronyms.
On takeoff, I use HAAPPY
Heading - matches runway
Ailerons - set for wind
Airspeed - alive, looking for rotation speed
Power - RPM or Manifold Pressure where it belongs
Pitch - Pitch up for rotation
Y - Aim for an airspeed slightly more than VY

On landing I use several versions of B-RAAGS
Entering Downwind
Boost Pump On if low wing
Report - announce entering downwind or if tower when they say to
Airspeed - 100 kts
Altitude - Pattern
Gear - Not yet
Scan - Look for traffic

Numbers
Runway - matches what I think it should
Airspeed - slowing
Altitude - Pattern
Gear - Down
Scan - Look for traffic

Turning Base
Report - if at uncontrolled field
Airspeed - slowing
Altitude - Descending 500 fpm
Gear - Check if they are Down
Scan - Look for traffic

Turning Final
Report - if at uncontrolled field
Airspeed - target for aircraft, usually 80 or 90 kts
Altitude - Adjust based on lights of VASI or sight picture
Gear - Check if they are Down
Scan - Look for traffic

Short Final
Runway - last chance to make sure you are landing on the correct runway
Airspeed - target for aircraft, usually 70 or 80 kts
Altitude - Adjust based on VASI
Gear - Check the gear light
Scan - Look for traffic

Over the Threshold
Airspeed - target for aircraft, usually 70 or 80 kts
Altitude - Adjust based on VASI or sight picture
Gear - Are you sure the gear are down?

I have target MP or RPM for each leg that I don’t repeat each time, I just set them and adjust as necessary for wind. Same thing for flaps, I put the first notch down at the numbers or final approach fix and the the rest near the threshold.

source: Stack Exchange

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sort: votes


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Why after 911; do we not have "fail-safe" transponders that cannot be turned off?
In the 911 terror attack the transponders were turned off.  Who is to blame for the lack of foresight that has allowed another jet liner to shut off their transponders.  This is a ¼ billion-dollar ship; it seems impossible that engineers would not be able to design a safe and reliable back up transponder system that would not jam other signals, and would not be a fire hazard.

See the answers on the linked duplicate. There is no such thing as an infallible design, nor is there such a thing as perfect construction/assembly/installation. As long as there is imperfection there is a non-zero chance of a failure, and as long as the chance of failure is not zero there will be a need to be able to completely disable any electronic component installed on an aircraft.

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What happens to the transponder, FDR and CVR in case of an explosion?
Will the above mentioned equipment still work and transmit data/location information if an explosion occurs inside the aircraft?

As ratchetfreak noted, the recorders don't transmit data, attached to them is a location beacon that operates for up to 30 days.
This location beacon isn't always successful in enabling searchers to find the recorders. In the case of AF447, it took two years before a search located the aircraft debris field on the sea floor and recovered it's recorders.
As for withstanding the stresses of an explosion, it obviously depends on the strength of the explosion and it's location in the aircraft. In the case of Pan Am 103, destroyed in flight by explosives, the recorders were recovered and data extracted.

A DFDR must obviously have a high degree of ‘crashworthiness.’ The first units were required to withstand a momentary shock force of 1,000gs, the latest test standards now call for a test to 3,400gs for a duration of 6.5 milliseconds. The units also have to withstand a static crushing force at all of its six axis points of an applied load force of 5,000lbs for 5 minutes on each axis. Third, it must withstand a 500lbs piercing force test conducted by dropping it onto a ¼ inch steel pin from 10 feet. Lastly it must withstand a 1,100°C fire test for 60 minutes, and a 260°C oven test for 10 hours.
It is also required that these units are mounted within the tail area of an aircraft, away from the potential crushing force of any engines mounted nearby. The DFDR must be watertight to a depth of 20,000 feet in sea water, and survive at this depth for 30 days - and it must be fitted with an underwater locator beacon which will act like a sonar transmitter, by ‘pinging’ a signal through the medium of water that it might be laying in.

From http://www.avbuyer.com/articles/detail.asp?id=1858

1G is the force you feel on your feet standing up.
12G is the most a fighter-jet pilot normally experiences in combat.
16G sustained for 1 minute will kill you.
25G for an less than a second will hospitalize a fit racing car driver

350G results in total body fragmentation

In a 727 crash landing

Impact forces at the front of the plane peaked at 12 G (12 times the force of gravity), in the centre the force was less, 8 G, at the rear it was 6 G, half that at the front and no greater than being hit in a fairground bumper car.

In a 720 crash,
the maximum force was 14 G vertically for 0.8 seconds

This F4 phantom striking a concrete block at 480 MPH produced average peak forces of less than 60 G (see fig 7). The most solid elements (the engines) experienced forces of up to 700 G (fig 11).

3400G is therefore a lot.

12g is what fighter pilots can manage with help of anti-g suit and good training. Without those anybody will be knocked unconscious much earlier.

The "total body fragmentation" link is broken.

@Sean: thanks, fixed.

To get a feeling of the dimensions, a depleted uranium tank shell impacting on tank armor is decelerated with around 10.000 G. So with 3400 G we're in that area of forces that high energy projectiles recieve on striking a target. And decelerating from 1000 m/s to 0 m/s at 10.000 G will take approx. 10ms. So you could almost launch these things out of a cannon and they would still survive.

FDR and CVR don't transmit anything they just record data onto a magnetic tape or in a solid state drive, when the plane crashes/explodes they become just part of the debris and wait until they get found. The boxes are rated to survive nearly any feasible aircraft crash.
The special case is if they get submerged, then the attached locator beacon will activate and send out pings for at least 30 days.
The transponder will likely not survive and it needs power to work either way.

Adding to ratched freak's answer: the underwater locator beacons have a survival rate of 90% spanning 27 air accidents over the sea. Previous to the BEA AF447 investigation the rate was believed to be 80%.

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Is it possible for the sensors which determine when an aircraft has landed in water to become damaged?
A plane has sensors that should transmit data back somewhere when it hits water correct? Is it possible that these can be turned off/damaged?

See also the answers over here: (http://aviation.stackexchange.com/questions/2406/what-happens-to-the-transponder-fdr-and-cvr-in-case-of-an-explosion).

The premise that the sensor "transmit[s] data back somewhere" is misleading. If it were easy to transmit data to a ground station, the aircraft would do it continuously. However, considerations like transmitter power required, lack of a proper antenna after a crash, the curvature of the earth, and the vastness of the oceans mean that the beacon can only send out a fairly weak tracking signal that can be heard only a few km away in good conditions.

Yes, the component in question is called the Underwater Locator Beacon.
They are not foolproof. To disable them manually you need physical access to the black boxes, which are located in the tail section of the plane.

A plane has sensors that should transmit data back somewhere when it hits water correct?

This isn't really correct.
CVR/FDR/ULB
The Cockpit Voice recorder (CVR) and Flight Data Recorder (FDR) don't transmit data. They do have attached to each of them an Underwater Locator Beacon (ULB) but this doesn't transmit data either. When submerged, it sends out a sonar ping every 50 seconds for up to 30 days. This sonar signal can be detected by an immersed sonar sensor in the near vicinity (maybe a couple of miles), not across thousands of miles of open ocean.
EPIRB/ELT
Ships/boats typically carry an Emergency Position Indicating Radio Beacon (EPIRB) designed to start transmitting a location signal to satellites when the ship or boat capsizes or sinks.
The aircraft equivalent is the Emergency Locator Beacon (ELT) but, in the USA, from what I've read, this is only mandated for small private aircraft.
Commercial planes that fly scheduled routes are not required to have an ELT (I imagine the regulators thought that ATC communication, transponders and ACARS would together provide adequate location data)
787s do have ELTs fitted, somewhat notoriously. I've seen nothing to suggest that 10-year-old 777s do.

Is it possible that these can be turned off/damaged?

ULBs cannot be turned off in flight - because they are not on. Since the CVR and FDR are at the rear of airliners the ULB is not accessible from the cockpit and probably cannot be easily disabled. A ULB would have to be disassembled (see 02:55 onwards).
The ELT, if carried, is typically fixed to the top of the aircraft and designed to break away if a plane sinks. I imagine this makes it difficult for the crew to access it and disable it in flight.

yes, ELTs can be damaged.


text:
What is a "Flight Director"?
What is a Flight Director, and how does it differ from Autopilot?

The flight director is related to the autopilot system. It displays a guide on the artificial horizon, which shows the attitude of the airplane, but does nothing to control the plane. The guide represents a reference of an airplane attitude that will follow the parameters set for the autopilot. The pilot can manually fly the plane directly where the flight director indicates, and by doing so the plane will follow the parameters set for the autopilot.
If the autopilot is engaged, autopilot flies the plane to follow the flight director. The flight director serves as a visual indication of where the autopilot wants the plane to go. Although a flight director typically accompanies an autopilot system, some aircraft have a flight director without an autopilot.
The procedure to engage them is to first turn on the flight director, which will show where the autopilot wants the plane to be, and then to engage the autopilot, which will then automatically fly the plane.
This is what the autopilot controls can look like.

Here is the Boeing flight director, visible as the crossed magenta lines in the center of the screen.

One minor comment:  To say that the flight director is part of the autopilot is not always true.  I've flown aircraft that have flight directors but no autopilots.  In many cases they are independant systems, with the autopilot just blindly following the flight director (within limits, usually).

Is it possible to have autopilot without flight director instead?

It lets the pilot know what the autopilot would do if it were flying instead, by displaying an indicator, usually a miniature pink plane or line, on the artificial horizon.
The difference between the autopilot and flight director is that the autopilot flies the plane, the flight director gives the pilot an idea of what the autopilot would like to do if it was in charge.

It's the traditional flight instruments, integrated to work in a complementary way. For example the steering bars moving across the face of the compass so as to give the pilot visual ques for turning onto a desired heading and/or altitude.
The flight director gives a visual display of the overall aircraft attitude in space. The flight director display reacts to inputs coming from, for example, heading dials, electronic flight plans, and actual aircraft movement. The flight director does not physically control the aircraft.
The autopilot physically controls the aircraft in response to essentially the same inputs. The flight director essentially does not care if a human or the autopilot is actually in control. The autopilot adds intelligence which allows for various levels of pilot non-intervention up to the point of virtually hands-off control from takeoff to landing.
Together, the flight director and autopilot permit the pilot to let his skills atrophy while inducing a sense of inferiority on the part of the pilot in command; thus permitting well controlled crashes.

Simply: Flight Director is a system that computes desired pitch and roll from parameters like heading, altitude, vertical speed. Then an autopilot computes control surfaces deflection from given parameters: pitch and roll.
So: Pilot sets altitude, heading for Flight Director.
Flight director then computes pitch and roll for Autopilot (and human pilot, too).
If Autopilot is engaged, then it computes control surfaces deflections and moves the surfaces.
Flight Director is also displayed on PFD in some way, so if Autopilot is disengaged, the human pilot can still fly to follow FD's directions.


text:
How is data transmitted to CVR and FDR?
A recent news item mentioned that "black boxes" are typically stored in the tail section of an aircraft to maximize their odds of surviving a catastrophic incident.
If they're stored in the rear of the aircraft, presumably flight data and cockpit voice data is transmitted via wires which run the length of the aircraft.
Aren't these susceptible to damage during an incident? There have been incidents of explosions and fires which damage flight control cables - aren't the FDR and CVR susceptible in the same way?

Storing them in the tail section is not what increases survivability. Check out the "How Its Made" episode about aircraft black boxes at https://www.youtube.com/watch?v=1NK_027e0u4. Interesting to watch if you're curious about this.

You are very correct that this can happen- If i'm not wrong, what happened during the last 6 minutes of Swissair Flight 111 will never be known for this reason.
In general however, by the time the fire would spread to this extent the CVR and/or FDR would probably have picked up some hint of fire and the reason. To increase survivability, the FDR and CVR are connected off separate power buses ('boards'), so I'd imagine the cables for each not exactly next to each other on the fuselage, and if one trips, the other one will hopefully still run for a bit longer.
The cockpit voice recorder operates a simple microphone I believe, so I'd expect that it wouldn't be much more complicated than your computer microphone. The data would probably be converted from analog to digital before being transmitted backwards.
As for the 88 parameters that the Flight Data recorder currently requires, I'd imagine that there would be a serial connection from each relevant part- each flight computer, engine etc. all leading to the back of the aircraft.
Source: FDR Handbook- NTSB

Actually, a few things that happened during those last six minutes are known (for instance, we know that the #2 engine was shut down about a minute prior to impact, thanx to the recovery of its FADEC's NVM modules).  In the main, however, your statement is correct - just nitpicking here.

Most airplanes implement data buses such as ARINC 429 which describes the physical interface and a standard protocol allowing different devices to communicate and exchange data with eachother.  The A380 and 787 use ethernet as the phyiscal layer but still use an ARINC defined protocol for communications over ethernet.
Just about all of the electronic parts of an airplane communicate over these buses as there are many sensors and the different devices need data from a different subset of those sensors.  What the flight data recorder, as well as FOQA (flight operations quality assurance) boxes do is tap into the data bus and record what is happening at regular intervals.
You are correct that the placement of these devices necessitate that the wiring for the data bus extends to the rear of the airplane.  This may not be the only reason though as in the rear of some airplanes you have engines, halon bottles, hydraulic actuators, smoke detectors, door sensors, pressurization controls (outflow valves).  The FDR doesn't need all of this data, but FOQA might use it and the EICAS system needs all of it, so the data bus will always extend the length of the airplane.   This does make it susceptible to damage, but so are the flight control cables, hydraulic lines, bleed air lines, fuel lines, etc that may also be routed to the rear of the airplane.


text:
How to choose an aviation headset?
I am currently working on my private pilot license and am using a headset from the flight school.  I am coming up to my first solo and thinking about purchasing my first headset.
There are many different types of headset on the market, so what should I look for in a headset, and how do I go about picking the right headset for me?

I've modified your question a little bit to make it more generic and less of a shopping ("Which headset should I buy?") question and more a "What do I look for?" question -- If you want to talk about specific headset brands you might want to stop by chat, I'm sure the folks there will have some recommendations.

Not to be cliche, but you really do get what you pay for.  A 100USD headset might work at first, but will lack the quality of something in the range of 350USD.  Similarly, a 350USD headset will work, and last a lifetime, but won't have the noise cancellation characteristics of a 1100USD ANR headset.  As for me, I have a 350USD David Clark headset and I love it, but in the future I would like to upgrade to Bose.

First, do not buy any headset without trying it on.  Ignore those who say My Brand is the best!  Heads come in different shapes and to get a headset that is comfortable for you, you must try it/them on.  If possible, borrow a different one for each flight you take before you decide.
Second, if you are at all serious about this flying thing, pay up to get ANR headsets.  "Active Noise Reduction" (ANR) comes with different names (ENC is another that you will see) but they all reduce noise by creating "anti-noise" which has the same wave form (but inverted) as the noise you would otherwise hear, thus cancelling it out.  ANR headsets cancel the noise in the lower frequencies (engine rumble, exhaust noise, etc.) but permit higher frequencies to come through so that hearing radios, speech over the intercom, etc. is not affected.
Remember, loud noise damages your hearing, and the effect of noise is cumulative over the years.  In most cases the hearing loss doesn't really manifest itself until later in life.  Act now to protect your hearing.  This is the reason that the diminishing number of WWII aviators are almost universally hard of hearing.

I'm probably one of the few people who isn't an ANR convert, mainly because I switched to in-ear headsets - you can get pretty excellent noise attenuation from those (-35 to -40dB in the low frequencies). For traditional earcup headsets though I agree ANR is a must-have

I am with Skip on the ANR.  I wish I would have done it sooner.  I now suffer from Tinnitus, ringing in the ears, due to a hearing loss.  The audiologist says my hearing loss is in the range they see for piston pilots.  I ended up with Bose headsets, and Dave Clark also makes some good units.  Both companies have excellent service and will often fix issues  (frayed cables, ripped pads, etc) for free.

@JerryKur The service from David Clark is particularly legendary - Folks have sent them decades-old headsets for repair and received completely refurbished units in better-than-factory-new condition.

@voretaq7: I use a DC ANR every time I fly (approaching 700 hours now).  I like the product and its reliability but your comment on their legendary service may be not true anymore.  The last time I requested a replacement foam mike muff I had to pay for it.  Oh the Horror!

Wow.  Sorry to hear you had to pay for the mike muff.  Maybe they have gone cheap.  With Bose I told them one of my gel earpads when felt a little flat and they FEDed me a replacement.  At Oshkosh Bose used to have a truck where they would refurbished your headset while you wandered around

The two main purposes of an aviation headset are making the cabin quieter, and making it easier to talk to ATC while keeping your hands free, so in selecting a headset you want to find one that will do both of those things very well.
To figure that out there are three major things you'll want to look at when picking a headset:

Noise Reduction Rating (NRR)
This value, expressed in decibels (dB), indicates how good the headset is at preventing cabin noise from reaching your ears.  A higher noise reduction rating cuts out more engine and wind noise (which prevents hearing damage and noise fatigue) and makes it easier to hear radio calls.
Higher values are better - a headset with a 30dB NRR is quieter than one with a 24dB NRR.

Noise reduction ratings may be expressed as a positive or negative number (it's attenuation, so negative is "more correct"). 24dB or -24dB means the same thing when reading specs.

Headset Style
There are three basic styles of headsets, and one type will probably most comfortable for you.
Earcup headsets have earcups that surrond your ear, like classic David Clarks.
In-Ear headsets have earbuds/eartips that fit into your ear canal.
Over-the-Ear headsets are like headphones and sit "over" your ear (mainly for quiet cockpits).

Weight
Self-Explanatory: You're going to have this thing on your head for the duration of your flight. Wearing a 20-ounce (0.6 kg) headset is more fatiguing than a 10-ounce (0.3 kg) one, and you might have some neck pain if the headset is too heavy.

Earcup headsets tend to be the heaviest - 12 to 24 ounces. Over-the-Ear headsets usually weigh in at 3-4 ounces, and in-ear headsets are generally 3 ounces or less.

Secondary things to consider include:

Do you prefer Active or Passive noise reduction?
Active Noise Reduction can make a very light headset extremely quiet, but requires power (battery or ships power) and cost a bit more.
What accessory functions would you like?
There are headsets with Bluetooth, headsets with music inputs, etc.

Ultimately the best way to pick a headset is to try several to see which you like best. You're evaluating them on some objective things ("How quiet is it?") but also a lot of personal/subjective things: "Is it too heavy?", "Do the earcups/eartips fit my ear well?", "Is the clamping force like having my head in a vise?", etc.
Your flight school may sell headsets, in which case ask to try a few different ones on your next few lessons to see which you like best. You can also chat with other pilots and try to get a ride with them to try out their headset (the exception to this often being in-ear headsets -- some folks get grossed out at the idea of having someone else's ear gunk on their tips).


text:
How does wing bending relief of an a340 compared to an a330 allow it to carry 30t more fuel in a center section of nearly identical wings?
From this question this reference in ymb1's answer states that the a340 and a330 have nearly identical wings.

Because of bending relief from the weight of its outboard engines, the bending moment of a four-engined aircraft is substantially lower than it is for a twin at the same maximum take-off weight. For the same fuselage weight, therefore, a twin needs a stronger, heavier wing than a quad.
It follows that, for the same wing, the payload carried in the fuselage must be less for a twin than a four, which is exactly what has happened with the A330/A340: the latter carries about 20% more payload. This translates to about 30t of extra fuel, giving the A340 its long-range capability and requiring the addition of a centre-fuselage undercarriage leg. Design strength required was "only 1% higher than the A330", says Jeff Jupp, BAe chief engineer, Airbus.

(Original: A330, A340)
The reference states that bending relief by having four engines instead of two is the reason 30t more fuel can be carried in a wing center tank.
How can moving 4t (per engine) outboard 10m create enough bending relief to add 30t in the center of the wing?

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
How do I clear an aircraft to exit a hold?
I'm learning ATC and one question is worrying me..
How do I tell a pilot to exit a hold and continue inbound...
Eg: pilot has entered hold and done one orbit.
and started the second,
and I want the aircraft to turn again 180 degree on inbound.
Basically how do I tell an aircraft to break out the stack, and continue flight plan.

Note that a hold and an orbit are different to one another.

This depends on what exactly you want the aircraft to do:
Immediately depart the hold and fly directly to another fix:

N1234 cleared to 'clearance limit' via direct 'fix' and then as previously filed.

Immediately depart the hold and fly an assigned heading:

N1234 Cleared to 'clearance limit' via radar vectors. Fly heading 'heading'.

Proceed to another fix after passing the holding point inbound:

N1234 After 'holding fix', cleared to 'clearance limit' via direct 'fix' and then as previously filed.

Fly the published approach after passing the holding point inbound:

N1234 Maintain 'altitude' until 'holding fix', cleared 'approach name'.

Altitude
Lastly, add the altitude to any of the above clearances if it is different than the current altitude by adding a climb/descend and maintain  'altitude' clearance.

Simply clear the aircraft to a new fix or provide vectors, depending on the situation. There's no need to explicitly state that they should exit the hold. If you'd like them to continue as per the flight plan, you can use something like (at least in the US):

NOVEMBER 368 JULIET ECHO, CLEARED TO (destination) VIA LAST ROUTING CLEARED [(further instructions)].

Reference: FAA AIM, paragraph 4-6-2

This is nothing against your answer (which is a direct quote from the AIM so should be correct), but I have never heard this clearance used. Instead I hear "as previously filed/cleared".

When you issue the hold you should give them an expect further clearance time, so that's one way to imply that they will be exiting.
Usually I hear ATC say "report procedure turn inbound" or in the case of your question, "report inbound to [the fix]" right after the aircraft turns outbound the second/third/nth time. When the pilot reports inbound, ATC might say "pass [hold fix] at or above [altitude]," but definitely "proceed on course/you're clear for the approach."
Sorry if my terminology is off, I haven't flown IFR in a while.


text:
What is the purpose of the winglets on the Socata TB-31 Omega vertical stabilizer?
Aérospatiale-Socata built a prototype of the TB-31 for the French Air Force, which never went to production:

Source: netAirspace.com, photo by miamiair
What is the purpose of the winglets at the top of the vertical stabilizer?

I'd guess those are localizer antenna with an aerodynamic dielectric fairing.  Many aircraft are fitted with similar designs

They are likely VOR antennas.  Many Bonanzas and Cessnas have these as well.  The V-tails have them on the fuselage under the V.

What you observe here are VHF nav antennas for a VOR receiver.  This antenna design is lower drag than wire whip antennas.
The antenna serves no aerodynamic purpose except to minimize its own drag profile.


text:
Do I need a checkride for an initial SIC A320 type rating?
I have an FAA A320 initial pilot-in-command (PIC) type rating but haven't flown the actual aircraft.
Currently I am undergoing the second-in-command (SIC) type rating. I have completed the ground school program, Fixed Base Simulator and the Full Flight Simulator exactly like the Practical Test Standards for PIC.
Do I now according to FAA need to do a check ride? Or should I be issued the SIC privileges?

A PIC type supercedes and SIC type.  An SIC type is really just a formalism of 121 initial first officer training to satisfy specific ICAO requirements.  A typical route to an SIC type is airline ground school, FFS and then company checkride (no APD, no DE, just a check airman) and the issuance of the SIC type.  If you already had a PIC type you'd go through the same training and company check (required by company approved training), but you wouldn't get an SIC type as you already have a PIC type.
The FAA shouldn't require anything out of you if you are PIC typed already.  The company may require you to do the full FO training and the FO company checkride as part of its own FAA approved requirements.  If you want a more specific answer, you could provide more details about how your training is being conducted or you could ask your facilities training department or director of training.


text:
Which portion of combustion energy is used to spin the compressor of a pure jet engine?
In level flight at constant speed, it is correct to assume that the quantity of energy created by fuel combustion (FE) is exactly extracted by the turbine section (ME) and is used solely to spin the compressor section?

In other words, the propulsive energy (E4) is equal to energy in air the aircraft encounters (E1).
If this assumption is incorrect, what is the correct relationship between energy quantities E1 to E4? Maybe two extremes could be used for illustration: No thrust (idle) and full thrust.

If E1 would be containing E4, you would have no thrust: thrust means that you are putting energy into the airstream. you want as much as possible of the fuel energy to go in (useful) energy of the airstream. useful energy is kinetic, useless energy is thermal. (sorry, going to bed, someone else will make an answer out of this)

@Federico the compressor also produces thrust in a turbofan..

@pericynthion: The question is only about pure jet engine, no low or high bypass ratio.

@mins, much of the thrust still acts on the compressor in pure turbojet. Fluid applies force due to pressure always perpendicular to the surface, so thrust can only be applied to aft-facing surface and those are only the compressor blades and the diffusor.

@Federico: Maybe E4=E1 and ME=FE would be true at idle power?

@mins, $ME$ is actually rather unrelated to anything else, because that energy just runs in a loop inside the engine. $E4 = E1$ would be true if the engine produced no net thrust, but all engines actually produce some even at idle.

@pericynthion and where does the energy used by the compressor comes from?

Why do you think Mechanical Energy ME is needed to spin the compressor? The diagram suggest that you think E1 + ME = E2, E2+FE = E3 and E3-ME = E4. That's a reasonable approximation, but it then follows immediately that E4 = E1 + FE. In a slightly better approximation, there's friction and some of the ME is needed to overcome friction losses in the compressor.

@MSalters: "Why do you think Mechanical Energy ME is needed to spin the compressor?": Work is required to compress air with blades and vanes, it must come from somewhere. In my opinion from the turbine discs via the shaft.

@mins: Correct : that's the reason why the turbine is connected via the shaft to the compressor. You seemed to have all the pieces to the answer already, I was a bit surprised why you still came up with the idea that E1=E4


text:
How is the climb gradient calculated?
I was part of a discussion about the differences between all engine climb gradients and one engine inoperative (OEI) climb gradients, and a colleague suggested that climb gradient can be calculated as
$G = \frac{T-D}{W}$
Where

$G$ is Climb Gradient as a percent,
$T$ is Thrust,
$D$ is Drag, and
$W$ is Weight.

This derivation was never really explained, and it doesn't really make sense to me.  He continues by stating that lift can be assumed to equal weight for small climb angles, so that his equation becomes
$G = \frac{T}{W} -\frac{D}{L}$
Where $L$ is Lift.
For some analyses, I can see using the approximation $W = L$, but since that is essentially assuming your climb gradient is 0, it doesn't seem prudent to use that assumption to calculate the climb gradient itself.
Has anyone seen these equations before?  Or is there a piece to this that I'm missing that someone could explain to me?

Lift exactly equals weight at any climb angle so long as the aircraft is in an unaccelerated climb.

Assuming that thrust is entirely in the direction of travel and the flight path angle is constant, the Lift is equal to the weight times the cosine of the flight path angle:
$L = W\cos(\gamma)$
For small $\gamma$, $\cos(\gamma) \approx 1$
E.g. for a flight path angle of 10 degrees, the error introduced by the approximation is ~ 1.5%

For unaccelerated climb, the sum of all forces in the along path direction cancel each other out:
$ T-D-W\sin(\gamma) = 0$
The gradient is $\tan (\gamma)$.
Again, for small angles, $\sin(\gamma)\approx\tan(\gamma)$
From there it is a small step to see that the calculation suggested by your colleague is acceptable for unaccelerated climbs at small flight path angles.

Ah yes, the $sin(γ)≈tan(γ)$ part is the bit I had forgotten, I follow it now.  Thanks for you help.

Excellent answer. However i didn't understand how you calculated the equation for unaccelerated climb. Could you elaborate on that a bit? Thanks in advance.

@RestlessC0bra Thrust is a force in the direction of travel, drag acts in the opposite direction. There is also a component of weight ( -sin(gamma) W) that counteracts the thrust. If there is no acceleration all these force must be in balance, hence their sum is zero.

If the flight is climbing without acceleration, with a particular value of γ (gamma), we have a particular ratio (T-D)/W.  What happens to aircraft if suddenly increasing or decreasing T  (thrust) ?

@d.pensopositivo Suddenly there will be an acceleration in the flight path direction which causes the speed to change. Since the line of thrust is often not though the centre of mass of the aircraft, it will also cause a pitch moment, causing the pitch angle to change. As a secondary effect, both the change of speed and the change of pitch angle will affect the lift and therefore the flight path angle with change, unless some form of pitch control will maintain the flight path angle.


text:
What are the differences between Lycoming and Continental engine designs?
Inspired by a discussion in chat.
Most GA piston singles are powered by either Lycoming or Continental engines.
The engine designs used by both manufacturers are broadly similar (4-cycle, horizontally-opposed, gasoline-powered, air-cooled), and they're both generally available with either carburetors or fuel injection, but I know they're not "identical products".
What are some of the differences between the designs used by the two manufacturers, and what practical implications do those choices have for pilots?

To put a bit of a finer point on it (and give a freebie answer element), I'm looking for things like "Continental engines typically suspend the carburetor below the engine, while Lycoming engines mount it to the oil pan. The Lycoming design transfers heat from the oil sump to the carburetor, which can reduce the chance for carburetor icing"

FWIW, in the 60s when I was learning to fly in Cessnas with Continental engines in the Pacific NorthWest, I was taught to never reduce the power significantly without first applying carburetor heat. When I checked out in a Cherokee 140 with it's Lycoming engine and did the same, the instructor (who I found out later had instructed only in Cherokees) asked me why I did that. When I explained, he told me it was unnecessary.

Lycoming engines have the camshaft above the crankshaft, and Continental engines have the cam below the crankshaft.  This seems to keep the Conti cams better oiled and therefore less susceptible to corrosion.

The larger Continentals have the alternator belt-driven off the back of the engine.
And Continental still builds the four-cylinder O-200, and a lightweight version of that engine, too.
Continentals cost more money.
Continental parts cost more money.
Continentals normally have more valve trouble than Lycomings.
Lycomings have better valves and guides.
A Lycoming usually has its carb mounted to the oil sump, either the bottom or rear, and feeds the cylinders via tubes cast into the sump and connecting tubing from there to the intakes. The heat of the oil wicks into the carb body and reduces the likelihood of carb ice.
Continentals mount the carb on a separate intake manifold that doesn't transfer that heat, so pilots trained on Lycs can get bitten by Continentals if they haven't been trained in the detection and management of carb ice.
The fuel injection systems used by Continental and Lycoming are somewhat different.
Continental numbers their cylinders back-to-front.
Lycoming numbers them front-to-back, and the staggering of the cylinders is opposite between the two.
Continentals, at least the smaller ones, have the right mag firing at the top plugs and the left firing the bottom.
One of Lyc's mags will fire the top plugs on one side and the bottom plugs on the other, with the other mag firing the rest.

Really, they just sorta look the same, with cooling fins on them and a propeller on the front and pistons inside that go up and down, and they both turn lots of money into smoke, but that's about it. If I was to buy one, it would be a Lycoming.

Source: Quora


text:
How do you find information about overnight parking at any airport that is not your home airport?
As a private pilot, how do you find information and plan an overnight stay at an airport other than your home airport? For example, where to park, how to get out of the airport?

If you add the airport in question you may gain more precise information.

Generally, you call the FBO(s) at the airport. They are often listed in the A/FD or if you want a digital source, airnav has them. If you use Fore Flight, they will also list many of them. They will also provide you with fuel information as well as anything else you may need to know about the airport.
At smaller airports, you may be limited to a single FBO. At larger airports it's usually worth to talk to all of them (depending on your needs) since there can often be large differences in prices. It should be noted that some FBO's may waive ramp fees if you purchase some minimum quantity of fuel. Some airports may also charge landing fees (which you will pay through the FBO). When I flew out of KPNE there was a $5 a day landing fee (as many TO/LD as you wanted).
Pro Tip: the internet is riddled with forums and user groups these days. You may find that a simple "Hey thinking of flying into XXX next weekend" will return you a gaggle of information about the airport and what to do. If you are really lucky, someone may even offer you a spot in their hangar (if they have room).

Another Pro Tip:  Most professional pilots that I know use either FltPlan.com or Ac-U-Kwik for FBO information.

5 bucks a day? wow. Practically any Class D or larger airport in the DFW metro charges 70 dollars per visit (and I'm not sure about long-term parking etc).

$5 is just the landing fee (charged by either the state of PA or the city of Philadelphia I think) Im not sure what the FBO's charge to park since I always rented their planes I never paid for parking.


text:
What is the best method to time your round out or flare in Cessna 172?
I am a student pilot and I usually round out too high and I am not sure why. Can somebody  guide me how to make decision whether I am too high or not.

rule of thumb is when you feel the ground effect.

How would ground effect feel?

It feels like the plane doesn't want to land on the runway, even with the power off and the nose slightly high.

Make sure your seat height is the same every flight. Not jus way your visual cues are the same and you'll learn what the proper flare height will be and just how much to pull the nose up to.

FAA-P-8740-48 (the FAA On Landings series) is an excellent reference. Read part 1 carefully and I think you'll be pleased with the results.

There are some good answers here. I would just like to add a few points:

I don't like this idea of feeling for ground effect. I think this is unreliable, and will be different in different aircraft and conditions. I can only imagine the aircraft in a steeper than usual descent when I think of this, and not detecting ground effect because you have flown through it and hit the ground - hard.
Try to memorise the picture on the ground before take off, when sat in the cockpit. This will help.
Be aware of your peripheral vision, particularly around the sides of the dash (if you can see the runway that is). So while you should be looking in the middle distance, when the sides of the runway reach the same level as you, you are there.
You should always have some sink rate, so flaring too much and flying level or climbing, is clearly not right. So for example, rather than just pulling back on the stick to flare, reduce power at the same time as flaring just a little. That should increase your sink unless you are still a bit fast (Actually, if it does not thats an indicator that you are a bit fast).

Finally, you see lots of pilots kind of "feeling for the ground" by pulling back and then easing off then pulling back some more. Eventually the aircraft runs out of airspeed and falls the last 5 feet or so and the landing isn't too bad. A better technique would be to fly to the runway, fly level a little while, and just trying to keep the aircraft level by gradually applying back pressure. The gradual reduction in speed does the rest.
Also relax! And practice! That's the hard bit given the cost of flying!
P.S. I'm not a flight instructor, my only claim to fame is successfully landing a full motion 737 sim once with no instruction apart from air traffic responding to my Mayday call and telling me to fly the initial approach at 170 and threshold 130 (and giving me vectors to the ILS). Hope this helps you though.

Also don't be scared of going a little slower if necessary when you are over the threshold, for example you might fly the approach at 70 aiming for 60 knots over the numbers. After you have reached the numbers at the correct height and speed, speed is irrelevant, you just fly the aircraft. If you watch short field landings on TV then the stall warner often just chirps when they touch down. This would be about 50-55 in the 172 from my memory so its pointless to try to flare and touch down at 60 - it still wants to fly at that speed.

This really has got me thinking. Hope nobody minds me commenting again. In my view what you are really feeling for is the seat of the pants feel. When you are going fast, pull back slightly, the aircraft responds firmly which you feel through your butt. As your speed slows, this effect gets less to the point at the stall, you pull back slightly and the opposite occurs - the aircraft falls out of your hands. Thats what you are really feeling for I think during the flare - the point at which the aircraft doesn't want to fly. If you don't do this you try to flare and the damn thing goes up again!

I've been watching videos of crosswind landings and it seems to me that in that kind of weather, feeling for ground effect might not be reliable. I also noticed aircraft nosing down to get their wheels on the runway, and in that situation ground effect probably isn't a good indicator anyway.
Some of those crosswind landings looked like they had a major sphincter factor, and the pilot might not have been able to feel the ground effect.

As I related, whatever the weather I don't think feeling for ground effect is a good concept. If its a gusty day is it ground effect, or a gust? In my view you feel the "lift" of the aircraft by carefully controlling the speed if anything as I explained earlier. Landing crosswind is a little different, you always flare (i.e. lift the nose), pushing forward is bad (unless wheel landing a tail dragger), but flying at a slightly higher speed and dropping it on (while still protected the nosewheel) Ive found works for me in strong crosswinds. Hope this helps.

In many of these extreme crosswind landings, I see the nose dip as if the pilot was trying to force the wheels onto the runway. Maybe it was the chaotic wind that caused it to look that way; you'd think that if a pilot got to thinking about doing this, he'd reject the landing and go around.

It might be the momentum of the aircraft from the descent - in a crosswind you don't flare quite so much, don't arrest all the speed of the descent, because you want to touch down a little above stall so you still have some control effectiveness, so you don't float along the runway waiting for the aircraft to sink.This momentum might make the nose drop a little. I'm not watching the videos you are obviously.. All I was saying is that to actually push the stick forward when you are landing is an incorrect move - its all about varying amounts of pulling the stick back, usually.

"Also relax! And practice! That's the hard bit given the cost of flying!" - that's 90% of the answer. Veteran pilots will screw up landings if this statement is not followed.

One thing I didn't explicitly mention is at the point of flare if you are looking in the middle distance and aware of your peripheral vision you should be able to see the sink rate. So relax and be as smooth as you can on the controls. Like others have been saying practice! Practice what? Practice trying to see the sink rate (but don't start to look until you are over the numbers, I usually watch a combination of things including airspeed up to that point). PC based flight sims don't do it for me because you don't get the same visuals or tactile feedback from the controls. So it is expensive.

The usual cause for flaring too high is that the pilot is looking at the runway in front of the propeller instead of down at the far end of the runway.
Next time you're up with your instructor, have him do the landing, and look at the far end of the runway while using your peripheral vision to judge your height above the surface.
On the next lap, you fly the airplane, and try to get the same sight picture, both in front of you, and in your peripheral vision.

Student pilot here, and this is an issue I've been wrestling with recently.  For many landings, my CFI has told me the same points:

Fly the plane down to the numbers (or other landing point. In a simulator, you could hold that heading, not flare, and you would crash exactly on the runway numbers).
Make sure your landing speed is the same every time (varying any parameters between each landing - especially for a student pilot - will make it difficult to get a feel for a "good landing")
Wait until you see the runway get really big, then begin your flare. Doing so beforehand will result in starting your flare too high. This is illustrated really well in  this video.
Savor the flare. The flare process is an iterative thing. The initial flare does not need a large pullback on the yoke. Small pullback, then wait for the plane to settle.  The next pullback on the yoke should be slightly larger, since the plane has slowed down. Again, wait for the plane to settle. By the end, the plane gently touches down on the main wheels; the yoke should be pulled all the way back, and the nose wheel touches down last.

A lot of these were just words, and I didn't understand what he meant; it took me a lot of practice before I internalized them, with a "oooh, that's what you meant." In my opinion, there are a lot of aspects of flying that are subtle, and can't be simply read; they're things that are internalized with practice.

Many students flare too high - instinct is to not fly into the ground. Don't get discouraged, it will come with practice.
For me it's not a time thing or a sight thing, but a feel thing. I found flying at night to be a great thing for my landings because you have to depend more on feel than you do visual cues. If you get used to a certain sight picture and you then go to a different airfield you can get thrown off by a wider or narrower runway.
Try closing your eyes and following through on the controls while your instructor lands, pay attention to the seat of the pants feel.

Interesting. What are you trying to feel? The ground effect? Can you describe the feeling to look for a bit?

i think its the small positive G that comes with arresting the decent

I also found this answer from this user cougar531 on Yahoo!Answers. It sounds very helpful; something I'll try on my next flight. I also have the same problem, hence my id.

Assuming you've made a stabilized approach (constant airspeed, stable rate of descent, and without the need for major control inputs) then the flare is just a matter of practice. I imagine as you get close to the runway (say roughly the same height above ground as a hangar roof) you will gradually reduce power to idle and pitch up from your nose-low approach attitude to a more nose-level attitude. This is often called the round-out and immediately precedes the flare. When I talk about a flare I am assuming you are already just a few feet above ground.
The flare, as you correctly stated, is the time when you gradually pitch up as the aircraft slows without climbing (ballooning). The purpose is to slow the airplane down and touchdown at the slowest possible speed. The difficulty you have with making the flare without ballooning is very common, and no matter what it will take practice. The best way to practice this is to sharpen your sense of vertical movement while landing. I recommend looking further down the runway--toward the horizon, and be aware of cues in your peripheral vision that your airplane is sinking or rising. Your peripheral vision is particularly useful when the aircraft nose blocks the horizon. Pay attention, and over time you will develop a feel for the aircraft's sink-rate.
In the flare you should increase pitch to keep the airplane barely sinking toward the ground--we're talking almost level. As the airplane slows in airspeed you will feel it sink. Increase pitch to all-but-stop the sinking. If you increase the pitch to the point where the airplane completely stops descending, then hold that pitch where it is until the airplane starts to sink again. If you pitch up too rapidly and the airplane starts to balloon, your best bet is usually a go-around, although very very slight balloons can sometimes be corrected by simply holding the pitch and waiting for more speed to bleed off and the airplane to sink again. In all cases, resist the urge to lower the pitch of the nose. Your airplane is still slowing down on its own, and lowering the nose will kill what little lift you have left and could set you on the pavement pretty hard.
The rate at which you'll have to pitch up in the flare will vary depending on the day, the weight of the airplane, your airspeed, winds, etc... Some days it will be very fluid and gradual, and on other days you may find yourself having to make a few quick pitch adjustments. But if you try to make your adjustments in response to how rapidly the aircraft is sinking toward the ground based on visual cues out the window, then you should have good luck.
Remember you a trying to control a one ton piece of aluminum flying at 50 mph within the precision of a few inches... it definitely takes practice! Have fun and good luck!

Also, I have found out while practicing landing recently that when I start my round out about the time the sides of the runway expand 'exponentially' in my peripheral vision, then I am rounding at a perfect height. I guess this is what people are talking about by meaning looking at the end of the runway. I had more than 20 landings since then and I had none that is rounded out too soon. I hope this helps someone.

Confirmed! A year later and here I am with a PPL and 50 hours flying with passengers with almost all good landings :-) I can confirm this technique really worked for me. With a lot of practice, after a while, rounding out and flaring had become very familiar to my muscle and sensory memory that I didn't need to think about the technique while landing anymore. I just needed to focus on the landing :-)

There are a few tricks to getting the roundout on a CE-172 right.  One of them are wheelies.
Yes wheelies.
The next time you fly with your instructor, coordinate with the CFI and request a high speed taxi down a runway from ATC or go to an untowered airport with a long runway.  Line the a/c up on the runway centerline and start a normal takeoff roll.  When the aircraft reaches 50 or so knots, reduce throttle and hold that speed while remaining on the ground.  Apply back pressure on the yoke until the nosewheel lifts off the ground but the main gear remains on the runway.  Hold that nose high attitude while remaining on the ground, both to get the feel for how much back pressure you need to maintain the nose high attitude and also take a mental photograph of what the runway looks like at that nose high attitude.  You will use this as a reference as where you want to be as you execute the roundout.  NOTE: Make sure you terminate this maneuver and come to a complete stop before you run out of runway!
The next exercise will be an extension of your low speed flight training in the landing configuration.  You will be flying a roundout at 1-2 feet above the ground right down the runway.  Request the option from ATC or practice at a local untowered airport with a long runway as before and set up for a normal landing approach.  As you enter the roundout, do not pull the throttle to idle but instead maintain enough power to maintain about 52-55 kts in the flare.  Pay close attention to the airspeed and the height of the aircraft above the ground, holding off a touchdown and keeping the airplane about 1-2 feet off the ground at all times.  If you touchdown inadvertently, hey it happens, and that's exactly what we are going to do in a normal landing anyway.  Just pay close attention to your airspeed to prevent a stall and don't let the aircraft get too high during the exercise.  As the end of the runway nears, apply full power smoothly and execute a go around.  Repeat this process several times until you feel comfortable establishing the airplane in the roundout like this.  After this transition back to doing a normal landing again.  You will fly the airplane just like you did during the roundout exercise above only this time the power will be at idle and you will hold this height and attitude until the airplane is exhausted of energy and settles onto the runway, generally after the stall horn whines a bit.
WARNING:  These exercises should be discussed with your CFI prior to attempting and should only be executed under the immediate supervision of your CFI, and not on a solo flight.
The C-172 is a great little trainer but like a lot of GA airplanes from that era, it takes quite a bit of throw in the control inputs during slow flight and flaring, which I'm not fond of, but that was the style of the 1950s and 60s.  With some practice, and a lot of bad landings to boot, you should be able to grease 'em most of the time.

No such thing as a CE-172.  The CE indicates a Cessna Citation, a jet.  The venerable Cessna Skyhawk is a C-172.

I don't think of round-out as at an altitude, I think of it as at a horizontal position.
If I'm established on the PAPI/VASI vertical guidance, then when the numbers are directly below me, and the Touchdown Bars are filling my windscreen, then its time to flare.
If you're flaring too high, its because you're flaring too soon.
(You can probably still see the numbers.)
(Obviously, adjust your flight ONLY WITH AN INSTRUCTOR)Try not judging altitude, but judging position and sight-picture.

Unfortunately relying on runway markings doesn't work so well on grass runways :-)  But your basic point about focusing on the sight picture is definitely correct

this is true with assumption that you had a pretty good stabilized approach.

I once had a student pilot whonwas taught to roundout and flare above the numbers.  If anything changed, they would flare too early or too late.  It took a lot of practice to break that bad habit.

For reference. I am a student pilot. Cleared for solo yesterday. Solo scheduled next week. Training in a DA20. For me, the widening of the runway is a good indicator but you have to recognize it before it happens. If you wait for it to happen, it's probably too late and you have to do a quick hard pull on the stick which could lead to a bounce, or possibly balloon.(Remember, we are talking student here) So point is, you have to feel it coming and start a slow round off as the widening is happening.(And calms the CFI too) Fortunately, my home field is 5000ft and there is plenty of runway to spare if you set it down anywhere close to the keys. Don't be afraid to hang there for a few seconds a few feet above and let the plane slow down....It will! It wont fall like a stone either unless you make a drastic control input. You are in ground effect. I have also found that my best landing were ones that I didn't think too much about. They just happened. Above all else, Have Fun and use your checklist.

Welcome to the site and good luck with your solo!

Good point thanks! I have read the topic and went on my next lesson and got exactly in a situation you described - I had to do very quick and hard pulls. Ended up ballooning etc :)

This video has been great help to me.
Timing Your Flare - Rod Machado

Interesting technique; but bear in mind this only works well for small aircraft where the flight crew sits only a few feet off the ground.  It will not work well in larger aircraft e.g. a 747, etc where the cockpit is 40+ feet off the ground during a correct roundout.

True. I have used this technique in piper and cessna with decent success.

The cue I was taught related to the visual effect of the runway "widening" as you arrived at the proper flare point. Mind you, this effect will occur at different altitudes depending on the runway width. I trained at a field where the main runway had a paved width of only 25ft. Visiting a larger airport with a runway say 200ft wide required a bit of an adjustment to avoid flaring too high. Nevertheless, it is possible to develop a "feel" (visual, not seat-of-the-pants) for your height over the runway based on the way the edges of the runway (or lines of runway lights) appear to widen out.

The only reliable way to land an aircraft close to the prescribed spot is my setting the pitch 4-7 degrees lower than the flare pitch before touchdown on final and short final. Then use power ( adding or subtracting)  to judge your glideslope. Plant the plane to stop it faster.
Note: adjust your pitch degrees and ultimately speed based on the gust componet for the day.
Some instructors teach to maintain speed a certain margin above stall speed but what happens is when you come to the threshold and than either use up the whole runway floating or flare to high. Have the pitch set near round out.

Don't "flare". I think the whole "flare" thing got started in World War II or something. I don't know, but ignore it.
The 172 is a tricycle gear aircraft that is designed for 3-point landings. You should not be "flaring" it. They called it the "land-o-matic" for a reason: you don't need to (and should not) "flare" it.
The error to avoid is landing on the nose wheel, which is why some instructors teach "flaring", but this is really bad practice and an example of overcompensation to a fault. Teaching students to "flare" a 172 to avoid a hard nose-wheel landing is a faulty and improper teaching technique that goes against Cessna's own guidance in the POH and in their flight manuals. The only requirement is that you land mainwheels first. Other than that you should be landing in a level attitude.
When instructors tell you to look "at the end of the runway" or whatever, that advice is just as bad. The majority of runways have a grade of some sort and many have significant gradients. Looking at the end of a runway with a gradient will cause errors. Where you should be looking is at the touchdown point, not the end of the runway.
Watch the touchdown
The whole key to landing is to know EXACTLY where you are going to touchdown. The touchdown point can be recognized because every point before it will be moving downwards in your vision, and every point after it will be moving upwards.
On final, establish your glideslope and adjust your touchdown point to be on the numbers. If you cannot recognize the touchdown point, do go-rounds until you can visualize the touchdown point (also called the "aiming point"). The touchdown point is that point that stays motionless on your windshield.
If your glideslope is anywhere near correct, your attitude will be correct automatically and you will land on the main wheels. There should be ZERO need to be flaring or doing anything weird. You should set that glideslope and land on that same glideslope on the touchdown point. Once you touchdown, ease the nose wheel down. No need to "flare". Good glideslope, good touchdown point, good landing. It's that simple.
Nosewheel Landings
Okay, if you understand the above, you might be asking: "Fine, I understand, but how do nosewheel landings happen then, if that is the bad thing?" Good question. Nosewheel landings happen when the pilot dives--a very bad thing. What happens is that they come in too high and react by pushing the stick hard forward, diving. Obviously if you do this, you are abandoning your glide slope aren't you? If you have a set glideslot and touchdown point, this should NEVER happen EVER. When somebody dives, it is because they do not even know what their touchdown point is, and consequently it turns out to be off the runway. Trying to force a landing when your touchdown point is off the runway is a bad idea, obviously. If you have cognizance of your touchdown point, you will never be in a situation where you feel the need to dive.

I think you are misspeaking when you say the Cessna 172 is "designed" for 3-point landings - in fact the POH specifically says to touch down on the mains first. What an airframe will tolerate (its limits) and what it is designed for (as a normal operating practice) are two different things. The fact that a 172 can be landed flat, and even slammed down with excessive sink rates, doesn't mean they're proper technique for landing that aircraft…

@voretaq7 The 172 and all tricycle gear aircraft are designed to be landed in a level attitude should be trimmed that way when in a landing configuration and you can read any design manual on such aircraft to verify that.

If you are going to assert that this is proper technique Tyler you should be able to produce a citation stating such. I have given you one from the manufacturer's pilot operating handbook that directly contradicts your claim, and I can produce other citations from different manufacturers. Grumman (on the AA5 series) in particular is explicit about the flare-and-derotate technique being appropriate (and flat landings have caused nosegear collapses with that castering fork).

@voretaq7 If you want to make your own answer recommending flaring techniques to the OP, fine, but I think I have made it pretty clear that for a 172, I disagree with the way a lot of instructors teach it and specifically I think "flaring" (nose high) landings in a 172 is unnecessary and poor technique. If you have some different opinion, make your own answer.

As Carl Sagan said, "extraordinary claims demand extraordinary evidence". What you're proposing here directly contradicts the standard techniques taught by instructors, described in the PHAK, discussed in AOPA articles etc. If you're claiming that they're all encouraging "bad practice" while you've found a much better way then I think you should a) understand why people are skeptical, and b) produce authoritative evidence that goes beyond your personal opinion.

Obviously this is an incorrect answer.


text:
How would we calculate the load factor on an aerial vehicle while landing due to sudden gust loads?
In order to design the landing gear (wheels and suspension) of our model Airship, [say "m" kg -expected mass], I wanted to know, is there any way to calculate the loads which might be experienced by the wheels on impact with the ground (taking into consideration the unexpected gust loads - with gust velocity downwards say "V-gust")•
For simplicity I am Modelling it as a rigid body for now.
Note:- I thought of one way to calculate it, using momentum transfer.
Rate of change of Momentum = Force = density(rho) x projected Area(A) x (V-gust)^2.
Hence,( Gust force + Weight -Buoyant Force) ÷ Mass (m) will give me resultant acceleration.
Q1. Is this a right approach to calculate load?
Q2. Even if it's right, is this the load the wheels will experience during impact?
Please help me clear my confusion.
Edit:- Basically I want my designed landing gear with a normal sink speed upto 3m/s to be able to endure the landing impact even in case of an additional vertical downward gust upto 10m/s at the moment of touching the ground.  This is as specific and clear I could get.

Q1 No, see Gurkans answer. Q2 No, see Peter's answer. The problem with downwards gusts is the mostly the added velocity of the ship, not the pressure due to downwards gusts. Also realize that the wind 'has to go somewhere', so close to the ground, pure vertical gusts are almost impossible, and instead they 'spread out' to a horizontal velocity.

You need at least the stroke of the tire-gear combination to calculate a load. If the airship contacts the ground with a velocity of $w$ and a mass of $m$, the impulse $m\cdot w$ needs to be absorbed by a force $F$ acting along the stroke $s$, as in $m\cdot w = F\cdot s$. Adding airship flexibility will greatly improve the accuracy of the result, because I suspect the hull will deform easily and add to the stroke.
If you need an example of how this is calculated for a Boeing 747, please click here.

I am sorry, i didn't understand. Why should we calculate stroke length first to calculate force, plus thats also a problem how do i calculate the resultant velocity during impact because i dont think that the velocity of vertical gust will become velocity of airship. I thought calculating acceleration would be more feasible.

@Manish: Your question is sufficiently vague, and gusts don't blow into or out of the ground. So the gust speed is less important than the sink speed of the airship. To absorb energy, some force has to do work along a distance. The force is the gear load, and the distance is the stroke. And if you don't know the sink speed of the airship, you have no chance to calculate the gear force.

@Manish Think of it like this: Gust leads to an increased downwards velocity (sink speed), leads to an increased momentum that should be absorbed over a stroke $s$, which leads to an increased force. Always think action->reaction, don't just multiply all quantities you have until the units match up.

@peter I do know my max. Sink speed and yes gusts definitely don't come from the ground rather i was mentioning the vertical gusts above the airship pushing it further faster downwards. And thats what my doubt is, if I dont know both force and stroke length how to proceed To calculate them. Is it a standard way to assume the stroke length?

@Sanchises What you wrote is exactly what i am asking to calculate, the reaction force. And I don't think i am blindly multiplying quantities. RhoAv^2 is a common way to calculate force due rate of change of momentum. I am asking if its practical to apply.

@Manish $\rho A v^2$ is when you change the momentum of a volume flow. This problem is a air friction problem, in which case Gürkan's answer applies. See also my comment under your question.

If the question is about calculating the aerodynamic load acting on an airship, the answer is independent of the flight condition: whether it's landing, before touchdown, or after touchdown.
The aerodynamic load around the airship due to any gust, depends on the shape of the airship. Simply stated, the additional force due to gust would be:
"CD * Ref_Area * V_gust"
This emprical formula gives a force, that must be reacted by the landing gears. However, note that, the main assumption is this: the gust is a steady airflow which is comparably larger than your Airship. In contrast, if the Airship is quite large, then the gust would probably affect only some local portion of the vehicle.

Yes the airship will be quite large. But i do not want drag, i am concerned about maximum load which the tyres might face in case of presence of any vertical gusts.

My answer is more applicable to small airships (<20m size). As size increases, the airflow will be more difficult to predict, and assumptions will not be as valid. Btw, vertical gusts do not occur that much when near the ground (they do occur at the center of wind shears, but otherwise they would be comparably slower than lateral gusts).


text:
How do aircraft rental companies charge while the plane is not flying?
I am looking for some general advice - this is specific to the UK but may be similar else where.
I know it is possible to hire a private aircraft, I see comments like this on club/rental sites all the time:

Fly ASG members can experience affordable personal air travel for the Channel Islands, France and beyond. Fly ASG offers their services of non chartered aircraft rental to engage customers with a new streamlined approach to business and leisure travel.

Many sites mention the brakes on - brakes off fee per hour, but say you took that trip to the Channel Islands, France, or beyond: how do these companies usually charge for the bit where you will presumably be parked while you work on your sand castles at the beach for the day?
Just to be clear I'm not asking about airport parking etc. but how the owner of the aircraft will charge when it is not flying.

Flying clubs and aircraft renters generally only charge for the time the plane is actually in use. In the U.S. at least, this is commonly measured using the Hobbs time (actual clock time used, triggered by oil pressure or some other indicator that the plane is "in use"), or by Tach time, which is a bit trickier but can very roughly be thought of as the amount of wear you've put on the engine. (Strictly speaking it's a count of the number of engine revolutions, converted to "hours at cruise RPM".)
For overnight or longer trips, it's common to find a minimum hourly usage per day. For example, if you take a plane on a 3-day trip, and your club/owner requires 2 hours/day, you will be paying for 2 x 3 = 6 hours of Tach / Hobbs / whatever time, even if you didn't actually use the plane that much. You'll pay for the higher of your actual usage or your minimum usage per day.
It's extremely rare in the U.S., but not unheard-of, to encounter an extra fixed fee per day for taking the airplane for more than one day. (I've never personally encountered a fixed fee like this.) I'm not sure if things are different in the U.K.
Hourly rates can also either be "wet" (the rate includes fuel: any amount you pay for fuel will be deducted from your rental fee when you return) or "dry" (the rate includes the airplane only and you must pay for fuel). "Dry" rentals may or may not also require you to pay for oil or other consumables used.
(This is general information. Of course, if your question is specifically about Fly ASG's policies and fee scales, your best bet is to contact them directly. I know nothing about them.)

Ah ok that's interesting. Would you say that the minimum hours per day would usually be higher than 2 or not? To me it feels like if they had the opportunity to keep it local and have it out for more hours then they would do so.

@connersz I have seen the "minimums" vary from 2-4 hours per day.

@connersz Sometimes they could make more money on a particular day by keeping it local, but then they wouldn't attract those pilots who want the ability to go on trips. It's a sacrifice to increase membership in the long run.

checked local club here. Rental rates assume 1/3 of time away from home to be airtime. So overnighting can get rather expensive (especially as rental rates are including the fuel the engine would use while flying, so if you're on the ground for 40 hours after a 4 hour leg, then another 4 hour leg back you're charged among other things for 8 hours of fuel you never used, which at avgas rates isn't cheap).

@jwenting So effectively an 8 hour/day minimum? Wow, that's by far the steepest I've ever heard of! That club must cater mostly to students.

@dvnrrs probably, or short term rentals of only a few hours. They do mention that if you rent for an entire weekend they charge a minimum of 3 hours a day (but apparently not for multiple entire weekdays).

In contrast, my current FBO rarely allows overnight trips on weekends/holidays because they're booked sunup to sundown with part-time students, but they have no minimum for workdays because the planes would be mostly idle anyway.  In short, you have to check with each FBO/club because policies will vary based on their specific clients'/members' needs.

What if i want to fly to another location and dont fly back? Is there any service like "the owner company is responsbile to fly the plane back?"

@demonguy it depends on the club and the reason why you don't come back. Obviously if you crashed the plane, it becomes an insurance matter. If there's a maintenance issue, the club will cover the maintenance and associated travel costs for the maintenance (but probably won't cover your personal expenses to get home another way, and may also charge you for the flight time to fly the plane home if you don't go do it yourself). If you got sick, you'd probably have to pay ferry costs for someone else in the club to go get the plane. Ask the club to find out their exact policy.


text:
What restrictions apply in international airspace?
What restrictions are there on a flight in international airspace? For example, if you fly into the Pacific Ocean more than 12 miles (or whatever the distance is) offshore, are you free to fly any speed (such as faster than sound), at any altitude, or in any weather? Are FAA regulations in effect?
Is anybody really "in charge" of this airspace? If not, how do airliners keep organized on intercontinental flights?

When a US registered pilot is operating in international airspace, he is bound by both the US aviation regulations (14 CFR) and ICAO Annex 2, as required by 14 CFR 91.703.  It also requires compliance with MNPS and RVSM airspace rules where appropriate.

Sec. 91.703 - Operations of civil aircraft of U.S. registry outside of the United States.
(a) Each person operating a civil aircraft of U.S. registry outside of
  the United States shall--
(1) When over the high seas, comply with
  annex 2 (Rules of the Air) to the Convention on International Civil
  Aviation and with Secs. 91.117(c), 91.127, 91.129, and 91.131;
  (2) When within a foreign country, comply with the regulations relating to
  the flight and maneuver of aircraft there in force;
  [(3) Except for
  Sec. Sec. 91.117(a), 91.307(b), 91.309, 91.323, and 91.711, comply
  with this part so far as it is not inconsistent with applicable
  regulations of the foreign country where the aircraft is operated or
  annex 2 of the Convention on International Civil Aviation; and]
  (4) When operating within airspace designated as Minimum Navigation
  Performance Specifications (MNPS) airspace, comply with Sec. 91.705.
  When operating within airspace designated as Reduced Vertical
  Separation Minimum (RVSM) airspace, comply with Sec. 91.706.
(b) Annex
  2 to the Convention on International Civil Aviation, Ninth
  Edition--July 1990, with Amendments through Amendment 32 effective
  February 19, 1996, to which reference is made in this part, is
  incorporated into this part and made a part hereof as provided in 5
  U.S.C. Sec. 552 and pursuant to 1 CFR part 51. Annex 2 (including a
  complete historic file of changes thereto) is available for public
  inspection at the Rules Docket, AGC-200, Federal Aviation
  Administration, 800 Independence Avenue SW., Washington, DC 20591; or
  at the Office of the Federal Register, 800 North Capitol Street, NW.,
  Suite 700, Washington, DC. In addition, Annex 2 may be purchased from
  the International Civil Aviation Organization (Attention: Distribution
  Officer), P.O. Box 400, Succursale, Place de L'Aviation
  Internationale, 1000 Sherbrooke Street West, Montreal, Quebec, Canada
  H3A 2R2.

Another unrelated FAA document explains it in plain language:

International Civil Aviation Organization (ICAO)
ICAO is an agency of the United Nations that originated from the
  signing of the Convention on International Civil Aviation in December
  1944 (referred to as the Chicago Convention). This organization was
  formed to promote the safe and orderly development of international
  civil aviation. The Chicago Convention produced International
  Standards and Recommended Practices (SARP) aimed at standardizing
  international civil aviation operational practices and services.
  Currently, these SARP's are contained in 18 annexes to the Chicago
  Convention. In particular, Annex 2, Rules of the Air, and Annex 11,
  Air Traffic Services, are pertinent to this paper as they relate to
  civil aircraft operations, the establishment of airspace, and air
  traffic control (ATC) services in international airspace. Although not
  addressed in this paper, it should be noted that the SARP's are
  augmented by various ICAO documents containing Procedures for Air
  Navigation Services (PANS) that amplify the basic principles in the
  SARP's. Further, to supplement the worldwide procedures contained in
  the annexes and PANS, ICAO develops Regional Supplementary Procedures,
  which are part of the Air Navigation Plans agreed upon to meet the
  needs of specific geographical areas.
Two articles of the Chicago Convention also have a bearing on the
  subject of this paper:
Article 3:
Exempts state-owned aircraft (which includes military aircraft) from
  the provisions of Annex 11 and its Standards and Recommended
  Practices. (Note: As an ICAO Contracting State, the U.S. has agreed
  that its state aircraft will be operated in international airspace
  with due regard for the safety of civil aircraft.)
Article 12:
Obligates each ICAO Contracting State to adopt measures to insure that
  persons operating an aircraft within its territory shall comply with
  that state's air traffic rules; or with Annex 2, Rules of the Air,
  when operating over the high seas. The U.S. satisfied this
  responsibility through Title 14, Code of Federal Regulations (CFR)
  Part 91 which requires that operators of aircraft comply with U.S.
  operating rules when in the U.S., and that U.S.-registered aircraft
  comply with Annex 2 when over the high seas (see section 91.703).
  However, section 91.703 applies only to civil aircraft, and state
  aircraft operating outside the U.S. are only subject to the "due
  regard" provisions of Article 3 of the Convention.
Under ICAO agreements, the SARP's in Annex 11 apply to airspace under
  the jurisdiction of a contracting state which has accepted the
  responsibility of providing air traffic services over the high seas,
  or in airspace of undetermined sovereignty.

The relevant FAA information is available here. As the page says:

The dynamics of oceanic and remote international operations are such
  that they are constantly evolving and it is incumbent upon the
  operators to closely monitor any changes

The general approach as I very roughly understand it is that ICAO defines general procedures, airspace etc. for international airspace but each country is responsible for ensuring that their aircraft comply, so if - for example - you want to cross the North Atlantic in an N-registered aircraft then you require FAA approval.
The North Atlantic Operations and Airspace Manual says:

Within this airspace a formal Approval Process by the State of
  Registry of the aircraft or the State of the Operator ensures that
  aircraft meet defined MNPS Standards and that appropriate crew
  procedures and training have been adopted.

The document does acknowledge that it's mainly aimed at airlines but it also states that it applies to GA flights too:

Aircraft without NAT MNPS or RVSM Approvals may, of course, also fly
  across the North Atlantic below FL285. However, due consideration must
  be given to the particular operating environment. Especially by
  pilots/operators of single and twin engine aircraft. Weather
  conditions can be harsh; there are limited VHF radio communications
  and ground-based navigation aids; and the terrain can be rugged and
  sparsely populated. International General Aviation (IGA) flights at
  these lower levels constitute a very small percentage of the overall
  NAT traffic but they account for the vast majority of Search and
  Rescue operations. Specific guidance for the pilots and operators of
  such flights was previously contained in the North Atlantic
  International General Aviation (NAT IGA) Operations Manual published
  by the FAA on behalf of the ICAO North Atlantic Systems Planning Group
  (NAT SPG). However, with effect from this Edition 2013, such guidance
  has been subsumed into this document.


text:
Is English sufficient for international aviation?
Is it possible to fly internationally understanding only English for radio communications? Are there exceptions?

ATC and pilots must be able to communicate in English on international flights involving ICAO member states. There are 191 countries that are members of the ICAO, covering almost all of the world.
While communications may be performed in the local language, English must be used upon request on international flights. Controllers and flight crew engaged in communications for international flights should be proficient in spoken English in addition to English aviation phraseology.
Some domestic airways and airports may require communications in the local language instead of English.
So English is sufficient if you stick to international airports and airways, but be sure to check the language requirements before you venture into foreign domestic airspace and airports.

ICAO has standardized on English (PDF), which "urges" (apparently it does not require?) contracting states (participating members) to use English for all communication. I believe proficiency standards implementation was originally set for 2008, but was pushed back to 2011.
The exceptions to this standard would be, most likely, any country which is not an ICAO member. For the most part, as of now flight in ICAO member countries should be possible if English is your only language, as the proficiency standards testing has been rolled out.

Personally speaking, I recently flew in Iceland, which has some forbiddingly-hard-to-pronounce names, but is an ICAO member state and which uses English for everything. It was a great, low-stress experience; air traffic controllers were very understanding and knew what I meant when I attempted to pronounce place names, even if I butchered them. Which I almost certainly did.

Prepare for a shock when you fly in France :-)

Fun :) I wonder if this is in violation of ICAO rules? It seems like it must be.

I'm sure it is, but the French don't care. I was shocked that even controllers on approach/departure frequencies had trouble using English.

I suppose Those of us who live in the FAA's glass house are not permitted to throw stones at other people's flaunting of ICAO recommendations :-)

At international airways and airports in France, English can be used, in accordance with ICAO rules. That is not always the case in domestic airspace and airports, which is allowed by the ICAO. For example, at LFPN when the tower is closed, only local aircraft can use the airport and communications must be in French.

I can only speak for Europe and the U.S. but be prepared to encounter controllers who only speak French when flying in France. As far as I know, France is the only country in Europe where English is not required for ATC. The same may be true for (former) French colonies but I don't know for sure.

I have flown to France several times, and while some of the controllers were very hard to understand, they technically did speak to us in English....

What happens if you can't speak French?

Then you have a real problem. Some radio operators (they're not real controllers) at small airports don't speak a single word of English. If you're flying into towered airports you should be able to communicate in (limited) English.